Support Guide

ABSTRACT

A support guide ( 11 ) for a transporting a flexible elongate substrate ( 13 ) is described. The support guide ( 11 ) comprises a support surface ( 17 ) and a fluid supply means for supplying a fluid between the support surface and the substrate ( 13 ). The fluid maintains the substrate spaced from the support surface ( 17 ) and the flow of the fluid between the substrate and the support surface causes a net longitudinal force on the substrate.

This invention relates to a support guide for flexible elongatesubstrates. In particular, this invention relates to a support guide forflexible elongate substrates on which electronic devices aremanufactured. In particular, the invention relates to a contact-lesssupport guide for roll-to-roll manufacturing equipment, for example foruse in continuous film processing

This invention also provides a transporting apparatus for transportingflexible elongate substrates (films) comprising at least one of thesupport guides and a manufacturing apparatus for manufacturingelectronic devices comprising at least one of the support guides.

A large number of electronic devices are manufactured by sequentiallydepositing multiple layers of microscopically aligned structures on asubstrate. For example, active matrix display devices are manufacturedby depositing a plurality of microscopically patterned and alignedlayers of conductors, semiconductors and insulators on a transparentsubstrate. Electronic devices manufactured in this way are susceptibleto defects caused by foreign particles becoming deposited on thesubstrate during the manufacturing processes. The foreign particlesbecome trapped between the layers and cause the electronic devices tomalfunction. To minimise the number of defects caused by foreignparticles, electronic devices are usually manufactured in a clean airenvironment known as a clean room.

Currently, most electronic devices manufactured by the above-describedmethod are manufactured on rigid substrates such as glass panels orsilicon wafers. However, there has recently been increased interest inmanufacturing electronic devices on flexible substrates such as thinplastic films.

Flexible substrates enable the use of reel-to-reel transporting in whichthe substrate is unwound from an unprocessed reel, passed through anumber of processing stages in which it is transported in differentdirections, and rewound onto a processed reel. The processing stagesmay, for example, include coating, printing, exposure, curing andetching stages. Reel-to-reel transporting is known as a low cost, massproduction technology that may provide significant productivity andefficiency improvements in the manufacture of electronic devices.However, there are a number of problems associated with the applicationof conventional reel-to-reel transporting technology to the manufactureof electronic devices.

Firstly, conventional reel-to-reel transporting employs a plurality ofrotatable rollers to transport the substrate. Although these rollersusually run on bearings, the rotational movement of the rollers andbearings is a source of foreign particle contamination in the clean airenvironment, and causes defects in the electronic devices beingmanufactured.

Secondly, in conventional reel-to-reel transporting, the surface of thesubstrate being transported comes into frequent contact with therotatable rollers. The layers of microscopically patterned and alignedstructures that are sequentially deposited on the substrate duringmanufacture of the electronic devices are highly sensitive to suchcontact, which may cause contamination or damage.

Thirdly, in conventional reel-to-reel transporting, most of the rollersare not driven. Instead, only the processed reel, onto which theprocessed substrate is wound, is driven. The tension in the substratethen pulls the substrate over the rollers in the processing stages, andunwinds the substrate from the unprocessed reel. Each of the processingstages and the unprocessed reel provide a resistance load on thesubstrate due to friction. The tension in the substrate consequentlyvaries along its length, being greatest at the processed reel end andleast at the unprocessed reel end. A certain amount of tension is alsorequired to bend the substrate around each roller. The differenttensions at each processing stage cause a different amount of stretchand creep in the substrate, and this limits the dimensional accuracy andresolution of the structures that are deposited on the substrate.Correct alignment of structures that are deposited in differentprocessing stages is also complicated by the varying tension in thesubstrate. Air rollers are known, but they use a lot of air which initself is highly disadvantageous in a clean room, invoke turbulence andare energy inefficient.

According to a first aspect of the invention, there is provided asupport guide for a transporting a flexible elongate substrate, thesupport guide comprising a support surface and a fluid supply means forsupplying a fluid between the support surface and the substrate, whereinthe fluid maintains the substrate spaced from the support surface andthe flow of the fluid between the substrate and the support surfacecauses a net longitudinal force on the substrate.

According to a second aspect of the invention, there is provided asupport guide for a transporting a flexible elongate substrate, thesupport guide comprising a support surface and a fluid supply means forsupplying a fluid between the support surface and the substrate, whereinan envelope of the support surface is substantially cylindrical, whereina portion of the support surface around which the substrate passes iscurved with a first constant radius of curvature, and a portion of thesupport surface at which the substrate enters or exits has radius ofcurvature which increases from the first constant radius of curvature toa second radius of curvature at which the support surface issubstantially straight.

The support guide thus supports the substrate without touching it, withthe substrate being supported by a cushion of fluid. The substrate maybe supported by the kinetic energy of the fluid or by the staticpressure of the fluid. By supporting the substrate in this way, the riskof contamination or damage caused by direct contact between the supportguide and the substrate can be eliminated.

The support guide of the invention does not rotate and has no movingparts. Consequently, when used in reel-to-reel processing applied to themanufacture of electronic devices, it does not cause any particlecontamination in the clean air environment, and defect rates may beminimised.

By providing a net longitudinal force on the substrate in accordancewith the first aspect of the invention at each support guide in areel-to-reel transporting system, the system may be arranged so thattension in the substrate is substantially constant throughout thesystem. This allows for improved dimensional accuracy and resolution ofstructures that are deposited on the substrate, and improved alignmentof structures that are deposited in different processing stages. The netlongitudinal force on the film is provided by shear stresses from thefluid flows.

By modified entry and exit regions in accordance with the second aspectof the invention, increased resistance to fluid flow can be provided,thereby reducing flow loss, and reducing contamination. In addition, byproviding a support region which extend until the substrate is straight,laminar flow can be obtained at the entry and exit regions, which alsoreduces turbulence.

In a preferred embodiment, the support guide is further for changing thedirection of travel of the substrate, and the support surface defines asubstantially cylindrical surface around which the substrate travels.The substrate is held in mechanical equilibrium by the tension in thesubstrate, which provides a net force towards the support surface, andwhich is opposed to a force of the fluid from the fluid supply means.

The fluid supply means may comprise at least one fluid supply channel,or jet, formed in the support surface to be covered by the substrate. Inthis case, the axis of at least one of the fluid supply channels may beat an angle to the normal of the support surface. Fluid may then bedirected towards the substrate at an angle to the normal of the supportsurface, thereby providing the net longitudinal force on the substrate.

The fluid supply means may alternatively or additionally comprise atleast one opening formed in the support surface to be covered by thesubstrate. In this case, the support surface may define the wall of achamber through which fluid is supplied, the fluid passing through theat least one opening. In embodiments, the area of the at least oneopening formed in the support surface may be at least 67%, preferably atleast 75%, and most preferably at least 80% of the area of the supportsurface that is to be covered by the substrate. The at least one openingformed in the support surface is preferably arranged so that it is to beoverlapped by the substrate at its edges.

In a preferred embodiment, the support surface has a varying radius atsubstrate entry and exit regions. In particular, the radius maygradually increase in a direction away from a central region of thesupport surface. In this way, fluid flow at the substrate entry and exitregions, and thus fluid loss, may be minimised. Reducing fluid lossimproves system efficiency and may help to maintain a clean airenvironment, particularly if the fluid is gaseous.

The substrate entry and exit regions of the support surface arepreferably adapted to provide differential fluid flow (fluid loss)between the support surface and the substrate, thereby providing the netlongitudinal force on the substrate. This may be achieved by providingdifferential spacing between the support surface and the substrate atthe substrate entry and exit regions.

For example, there may be greater spacing between the support surfaceand the substrate at the substrate exit region than at the substrateentry region, thereby providing the net longitudinal force on thesubstrate in the forward direction. Alternatively, there may be greaterspacing between the support surface and the substrate at the substrateentry region than at the substrate exit region, thereby providing thenet longitudinal force on the substrate in the backwards direction.

The fluid supply means may be a pressurised gas supply means, such as apressurised ionised air supply means, or alternatively a pressurisedliquid supply means.

The invention also provides a transporting apparatus for transportingflexible elongate substrates and a manufacturing apparatus formanufacturing electronic devices, each comprising at least one of thesupport guides of the invention.

The invention also provided a method for transporting a flexibleelongate substrate, the method comprising: passing the substrate over asupport surface; and supplying a fluid between the support surface andthe substrate, wherein the fluid maintains the substrate spaced from thesupport surface and the flow of the fluid between the substrate and thesupport surface causes a net longitudinal force on the substrate.

Throughout this description the terms “length” and “longitudinal” areused to refer to the direction of travel of the elongate substrate. Thedirection of travel of the substrate may change, for example, as ittravels around the support guide. Consequently, the longitudinaldirection may also vary.

Preferred embodiments of the invention will now be described by way ofexample only with reference to the accompanying drawings, in which:

FIG. 1 is a diagram of a manufacturing apparatus that employsreel-to-reel technology to transport a substrate;

FIG. 2 is a diagram of a support guide according to the invention;

FIG. 3 is a diagram showing the geometry at the substrate entry and exitregions of the support guide;

FIG. 4 shows one example of support guide of the invention;

FIG. 5 is a diagram showing the longitudinal force on the substrate; and

FIGS. 6(a) and 6(b) are diagrams showing alternative support guidesaccording to the invention.

The present invention relates to a support guide for use in reel-to-reeltransporting. An apparatus for manufacturing electronic devices mayemploy reel-to-reel transporting, and such an apparatus 1 isschematically shown in FIG. 1. The apparatus comprises an unprocessedreel 3 from which an unprocessed flexible elongate substrate is unwound,and a processed reel 5 on which the processed substrate is wound.Between the reels 3, 5 are a number of processing stages 7. Theprocessing stages each comprise a number of support guides over whichthe substrate is passed, and processing equipment (not shown) forprocessing the substrate. The processing equipment may, for example,include equipment for printing, exposure, curing or etching thesubstrate.

FIG. 2 shows a support guide 11 according to the invention. Theprocessing stages 7 shown in FIG. 1 may comprise several of the supportguides shown in FIG. 2. FIG. 2 also shows a flexible elongate substrate13 to be supported by the support guide 11. The substrate may be a PETfilm having a width of approximately 1 meter, a thickness ofapproximately 200 microns, and a Young's modulus of approximately 5 GPa.

Referring to FIG. 2, the support guide 11 comprises a thin walledcylindrical vessel 15. The cylindrical vessel has a length ofapproximately 1 meter and a radius of approximately 5 centimeters. Theouter surface of the cylindrical vessel 15 forms a support surface 17.In use, the substrate 13 travels around the support surface through anangle of approximately 180°.

FIG. 2 shows schematically a fluid supply means 18, which will comprisea pumped fluid source.

It can be shown that the tension required in the substrate to bend itaround the support guide may be calculated according to the followingequation: $\begin{matrix}{F = \frac{w\quad E\quad d^{3}}{12\quad R^{2}}} & {{Equation}\quad 1}\end{matrix}$where w is the width of the substrate, E is the Young's modulus of thefilm, d is the thickness of the film and R is the radius of curvature ofthe substrate/support guide.

For the substrate and support guide described above, a tension of 1.3 Nis required to bend the substrate around the support guide. For aprocessing stage comprising a large number of support guides, the totaltension may be considerable.

The cylindrical vessel 15 of the support guide is supported at its endsby brackets (not shown). The supporting brackets prevent any rotationalmovement of the cylindrical vessel.

The cylindrical vessel 13 has an opening 19 formed in the supportsurface 17. The opening 19 is substantially rectangular in shape(although it could of course be different in shape) and is completelycovered by the substrate 13 traveling around the support surface 17. Thewidth of the opening 19 is smaller than the width of the substrate 11,so that the substrate 13 overlaps the edges of the opening 19.Similarly, the length of the opening 19 is smaller than the length ofthe portion of the substrate 13 around the support surface 17 (i.e. itextends around less than 180 degrees in this example), so that an entryand an exit region are defined at the lengthwise ends of the opening 19.

The cylindrical vessel 15 has a pressurized air inlet manifold (notshown) at one end. Pressurized air is supplied to the cylindricalchamber through the pressurized air inlet manifold. In use, thepressurized air flows through the opening 19 in the support surface 17to provide a cushion of air between the support surface 17 and thesubstrate 13, thereby supporting the substrate 13.

The support surface 17 comprises a substrate entry region 21 and asubstrate exit region 23. The substrate entry region 21 is the region ofthe support surface 17 at which the substrate 13 begins to travel aroundthe support guide 11. The substrate exit region 23 is the region of thesupport surface 17 at which the substrate 13 begins to travel away fromthe support guide 11.

The outer envelope of the support surface 17 is substantially circularin cross section. However, according to the invention, the substrateentry and exit regions 21, 23 of the support surface 17 have adaptedgeometry, as shown in FIG. 3.

In particular, the substrate entry and exit regions 21, 23 of thesupport surface are extended in order to minimize the flow (loss) ofpressurized air from the cylindrical vessel 15 between the supportsurface 17 and the substrate 13. This is achieved by providing a supportsurface 17 that closely follows the shape of the bent substrate at thesubstrate entry and exit regions 21, 23.

FIG. 3 shows a cross section of the substrate exit region 23 of thesupport surface 17 in detail. The arrow 29 indicates the direction oftravel of the substrate 13. The solid line 25 represents the adaptedgeometry of the substrate exit region 23. It can be seen that thegeometry of the support surface in this region diverges from thecircular geometry 27 on which the central region of the support surfaceis based. Essentially, the radius R of the support surface increases atthe exit region 23.

The adapted geometry 25 provides a narrow gap between the supportsurface and the substrate. Compared to an arrangement in which thesupport surface has wholly circular geometry, the length (in thesubstrate movement direction) of the gap, i.e. the longitudinal distanceL from the edge 30 of opening 19 in the support surface to the pointwhere the support surface and substrate diverge, is elongated, therebyminimizing airflow (air loss). The gap is preferably of a substantiallyconstant height.

The entry and exit portions of the support surface start with the samecurvature R as the main envelope of the support surface, but thecurvature then increases to infinity so that the support surface islocally straight at the entry and exit region. The elongated entry andexit regions give increased resistance to fluid flow and also providelaminar flow.

As well as minimizing airflow, the geometry of the support surface 17 atthe substrate entry and exit regions is preferably adapted to provide anet longitudinal force on the substrate 13 traveling around the supportguide, thereby propelling the substrate around the support guide. Thisis achieved by adapting the geometry of the support surface 17 toprovide differential airflow (air loss) at the substrate entry and exitregions 21, 23, with the result that a differential force is exerted onthe substrate. In particular, the geometry at the substrate entry andexit regions 21, 23 is adapted so that, in use, the spacing between thesupport surface 17 and the substrate 13 is larger at the substrate exitregion than at the substrate entry region.

It is possible to provide different spacing at the entry and exitregions by taking advantage of the fact that the substrate seeks amechanical equilibrium. This mechanical equilibrium will correspond tothe air pressure decreasing linearly over the length of the gaps at theentry and exit regions. This defines the local curvature and shape ofthe substrate.

FIG. 4 shows an example of the cross sectional shape of one example ofsupport. As shown, the entry region 21 is relatively thin and short, andthe exit region 23 is relatively wide and long. The entry and exitregions are both sufficiently long to provide laminar flow.

FIG. 5 shows a diagram of the space, or gap, defined by the supportsurface 17 and the substrate 13 at the substrate entry or exit region21, 23. Air flows from an area of high pressure 33 adjacent the opening19 to an area of ambient pressure 35 where the substrate diverges fromthe support surface. The shear force supplied to the support surface orthe substrate is given by the following equation:2F_(w)=ph   Equation 2where F_(w) is the shear force, p is the pressure difference and h isthe height of the gap.

It can be seen from equation 2 that the shear force is proportional tothe height of the gap. Consequently, by providing gaps of differentheight at the substrate entry and exit regions, 21, 23, a netlongitudinal force on the substrate 13 can be provided. This force maybe in the direction of travel, thereby reducing tension in thesubstrate, or alternatively against the direction of travel, therebyincreasing tension. The latter arrangement may be advantageous forprocessing stages where a high substrate tension is required.

The shear force supplied to the support surface or the substrate is notdependent on the length of the gap between the support surface and thesubstrate. Accordingly, the geometry of the support surface may beadapted further so that the gap having the greater height is alsolonger. The greater length reduces airflow (air loss), and goes some wayto compensating for the increased air loss caused by the gap having agreater height.

FIG. 6(a) shows an alternative support guide according to the invention.This support guide is similar to that shown in FIG. 2. However, insteadof the fluid supply means comprising an opening formed in the supportsurface, the fluid supply means comprises a plurality of pressurized airchannels, or jets 31, formed into the support surface 17. The jets 31supply pressurized air between the support surface 17 and the substrate13. This pressurized air maintains the substrate 13 spaced from thesupport surface 17, either through the kinetic energy of the air orthrough its static pressure. The jets are also positioned in the supportsurface so that their axis is at an angle to the normal of the supportsurface. The pressurized air from the jets travels towards the substrate13 and impacts the substrate at an angle to its normal, thereby causinga net longitudinal force on the substrate. This longitudinal force mayeither be in the direction of travel of the substrate or against thedirection of travel of the substrate. The geometry of the supportsurface 17 at the substrate entry and exit regions may also be adaptedas described above with reference to the support guide shown in FIG. 2.

Other support guides according to the invention may provide a flatsupport surface, with the substrate traveling across the support surfacein a straight line. In this case, it is not possible to use tension inthe substrate to maintain the substrate in mechanical equilibrium.Accordingly, support surfaces 17 may be provided on either side of thesubstrate 13, as shown in FIG. 6(b). In this case, the fluid from thefluid supply means of each support surface 17 provides an equal andopposite force on the substrate 17 in a direction normal to thesubstrate surface, although additional measures may be required toensure stability of the substrate. Various modifications may be made tothe support guides according to the invention. For example, the supportguides may be adapted for use with pressurized liquids, such assolvents, instead of pressurized air. Such support guides may be usedin, for example, etching process equipment. Also, the fluid supply meansmay comprise a combination of openings and channels, or jets.

A small number of specific examples have been given above, but it willbe apparent to those skilled in the art that the invention can beadapted in numerous ways. For example, the roller of the invention canbe designed for redirecting a web through any desired angle for exampleas shown schematically in FIG. 1, not just 180 degrees as in the exampleabove. The various features described above may be used in differentcombinations to those shown.

1. A support guide (11) for a transporting a flexible elongate substrate(13), the support guide comprising a support surface (17) and a fluidsupply means (18) for supplying a fluid between the support surface andthe substrate, wherein the fluid maintains the substrate spaced from thesupport surface and the flow of the fluid between the substrate and thesupport surface causes a net longitudinal force on the substrate.
 2. Asupport guide (11) for a transporting a flexible elongate substrate(13), the support guide comprising a support surface (17) and a fluidsupply means (18) for supplying a fluid between the support surface andthe substrate, wherein an envelope of the support surface issubstantially cylindrical, wherein a portion of the support surfacearound which the substrate passes is curved with a first constant radiusof curvature (R), and a portion (21,23) of the support surface at whichthe substrate enters or exits has radius of curvature which increasesfrom the first constant radius of curvature (R) to a second radius ofcurvature at which the support surface is substantially straight.
 3. Thesupport guide as claimed in claim 2, wherein the portions (21,23) of thesupport surface at which the substrate enters and exits each have theradius of curvature which increases from the first constant radius ofcurvature to the second radius of curvature.
 4. The support guide asclaimed in claim 3, wherein the lengths of the portions (21,23) of thesupport surface of varying curvature at which the substrate enters andexits are different.
 5. The support guide as claimed in claim 1, whereinthe fluid maintains the substrate spaced from the support surface (17)and the flow of the fluid between the substrate and the support surfacecauses a net longitudinal force on the substrate.
 6. The support guideof claim 5, further for changing the direction of travel of thesubstrate, wherein part of the support surface (17) defines asubstantially cylindrical surface around which the substrate travels. 7.The support guide of claim 6, wherein the fluid supply means comprisesat least one fluid supply channel (31) formed in the support surface tobe covered by the substrate.
 8. The support guide of claim 7, whereinthe axis of at least one of the fluid supply channels is at an angle tothe normal of the support surface, thereby providing the netlongitudinal force on the substrate.
 9. The support guide of claim 6,wherein the fluid supply means comprises at least one opening (19)formed in the support surface to be covered by the substrate, thesupport surface (17) defining the wall of a chamber through which fluidis supplied.
 10. The support guide of claim 9, wherein the area of theat least one opening (19) formed in the support surface is at least 75%of the area of the support surface to be covered by the substrate (13).11. The support guide of claim 9, wherein the at least one opening (19)formed in the support surface is arranged to be overlapped by thesubstrate at its edges.
 12. The support guide of claim 6, wherein thesupport surface (17) is adapted to provide differential fluid flowbetween the support surface and the substrate at the substrate entry andexit regions (21,23), thereby providing a net longitudinal force on thesubstrate.
 13. The support guide of claim 12, wherein the supportsurface is adapted to provide the differential fluid flow by providingdifferential spacing between the support surface (17) and the substrate(13) at the substrate entry and exit regions (21,23).
 14. The supportguide of claim 13, wherein the support surface is adapted to providegreater spacing between the support surface and the substrate at thesubstrate exit region (23) than at the substrate entry region (21),thereby providing a net longitudinal force on the substrate in theforward direction.
 15. The support guide of claim 13, wherein thesupport surface is adapted to provide greater spacing between thesupport surface and the substrate at the substrate entry region (21)than at the substrate exit region (23), thereby providing the netlongitudinal force on the substrate in the backwards direction.
 16. Thesupport guide of claim 12, wherein the support entry or exit region thatis adapted to provide the greater spacing is longer.
 17. The supportguide of claim 1, wherein the fluid supply means (18) is a pressurisedgas supply means.
 18. The support guide of claim 1, wherein the fluidsupply means (18) is a pressurised liquid supply means.
 19. The supportguide of claim 1, for transporting a flexible elongate substrate (13) onwhich electronic devices are manufactured.
 20. A transporting apparatus(1) for transporting flexible elongate substrates, the transportingapparatus comprising at least one of the support guides (11) of claim 1.21. A manufacturing apparatus for manufacturing electronic devices, themanufacturing apparatus comprising the transporting apparatus (1) ofclaim
 20. 22. A method for transporting a flexible elongate substrate,the method comprising: passing the substrate (13) over a support surface(17); and supplying a fluid between the support surface (17) and thesubstrate (13), wherein the fluid maintains the substrate (13) spacedfrom the support surface (17) and the flow of the fluid between thesubstrate and the support surface causes a net longitudinal force on thesubstrate.
 23. The method of claim 22, further for changing thedirection of travel of the substrate, wherein the support surface (17)defines a substantially cylindrical surface around which the substratetravels.
 24. The method of claim 23, wherein the fluid is suppliedthrough at least one fluid supply channel (31) formed in the supportsurface and covered by the substrate.
 25. The method of claim 24,wherein the axis of at least one of the fluid supply channels (31) is atan angle to the normal of the support surface, thereby providing the netlongitudinal force on the substrate.
 26. The method of claim 23, whereinthe fluid is supplied through at least one opening (19) formed in thesupport surface and covered by the substrate, the support surfacedefining the wall of a chamber through which fluid is supplied.
 27. Themethod of claim 23, further comprising providing differential fluid flowbetween the support surface and the substrate at substrate entry andexit regions (21,23), thereby providing the net longitudinal force onthe substrate.
 28. The method of claim 22, wherein the fluid is apressurised gas.
 29. The method of claim 22, wherein the fluid is apressurised liquid.
 30. The method of claim 22, for transporting aflexible elongate substrate on which electronic devices aremanufactured.